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The Chicago
Hallucination
Assessment
Tool
User Guide
Sarah Keedy, Ph.D.
Barrett Kern, Psy.D.
CHAT USER GUIDE
Chicago Hallucination Assessment Tool (CHAT)
Summary

CHAT is a 30 minute semi-structured interview designed to quantify dimensions of
hallucination severity.

CHAT overlaps and expands the gold-standard PSYRATS-AH (Haddock et al., 1999)
which assesses severity of auditory hallucinations by rating aspects of hallucinations
with scales of 0-4.

Can capture Current (last couple of days) and/or Past/Worst hallucination experiences
in each modality.

Conceptualizes “Severity” along 3 dimensions and provides scores for each
dimension as well as a total score for each sensory modality, at different time points if
desired.
Dimensions of Hallucination Severity:
1. Physical
2. Cognitive
3. Emotional
Sum 1-3 for Total Severity score

Can capture treatment response history and other hallucination characteristics, if
desired.
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CHAT USER GUIDE
About the CHAT
The Chicago Hallucination Assessment Tool (CHAT) is a semi-structured
interview designed to gather quantitative, and optionally qualitative, information
regarding the severity of hallucinatory experiences. The target population for its use is
psychiatric patients. The CHAT is structured in two primary parts. The first is a series of
screening questions for hallucinatory experiences in each sensory modality to determine
which types of unusual perceptual experiences across the five senses may be
hallucinations and should be assessed further. Second, follow-up questions solicit
detailed information to help clarify whether experiences are hallucinations and then to
quantify their severity. Severity is quantified within each sensory modality as a sum of
the item scores, and can also be broken down to scores along three dimensions: Physical,
Cognitive, and Emotional severity.
Conceptually, the CHAT implements the notion that multiple sensory modalities
should be assessed for hallucinatory experiences, as is the case in the Scale for the
Assessment of Positive Symptoms (SAPS, Andreasen, 1984). The CHAT combines this
with the detailed severity assessment approach for a specific symptom, as implemented in
the Psychotic Symptom Rating Scales (PSYRATS, Haddock et al., 1999). CHAT items
draw from and build on the PSYRATS-Auditory Hallucination scale. The CHAT is not
designed to be highly sensitive to very occasional, unusual perceptual experiences such
as may be closer to normative experiences across the entire adult population. On the other
hand, some information about such experiences may be captured by the CHAT.
Additional key features of the CHAT include options to rate current and
past/worst experiences with hallucinations, treatment responsiveness, chronicity, and to
gather data on a range of qualitative features of hallucinatory experience.
Defining Hallucination
For the purposes of the CHAT, a hallucination is defined as a “sensory perception
that has the compelling sense of reality of a true perception but that occurs without
external stimulation of the relevant sensory organ" (American Psychiatric Association,
1994, p.767). An interviewee’s level of insight, level of intelligence, and verbal
expression abilities should be taken into consideration when evaluating descriptions of
possible hallucinatory experiences. Raters should be mindful of over-pathologized
descriptions of normal perceptions (e.g., thinking one’s name has been called when it has
not) as well as minimized accounts of hallucinatory experiences by patients with limited
insight, paranoia, or other reluctance to report an experience. The CHAT does not
require a diagnosable psychiatric condition to be identified in order for an individual to
report what may be classified as a hallucination, and unusual perceptual experiences rated
on the CHAT may or may not clearly be hallucinations. The CHAT includes a place
where the rater can record a judgment about the probability of a reported experience
being a hallucination as defined here, but this does not impact the ratings themselves.
Users of this instrument may wish to make a determination of how to incorporate such
decisions into their use of the scale.
Similar to many symptom rating scales, the CHAT is not a test with established
normative scores to help establish diagnoses, degree of abnormality, or other clinically-
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CHAT USER GUIDE
relevant constructs. Rather, the CHAT provides a quantitative score designed to describe
severity of hallucinations that may be useful for a variety of research purposes.
Interviewer Qualifications
The interviewer/rater should have clinical training and experience working with
individuals with psychiatric illnesses. The critical skills needed include familiarity with
psychiatric symptoms, and capacity to listen to patients describe their symptoms and
assess such descriptions against objective criteria, similar to skills utilized in the
diagnostic process or with other symptom severity assessments. Competent CHAT raters
will know how to 1) probe for additional information to determine the appropriate rating
for a given item, and 2) rephrase a question to allow different interviewees to understand
the intent of the question, consistent with the concept of a semi-structured interview.
Further, the interviewer should have appreciation for individual differences and variation
in how hallucinations, as with many psychiatric symptoms, may be understood, labeled,
or talked about by those experiencing them.
Severity Scales of the CHAT
A principle feature of the CHAT is to operationalize “hallucination severity” by
scoring along three dimensions: Physical, Cognitive, and Emotional. The Physical
dimension includes items related to the physical characteristics of a hallucination, such as
frequency, duration, and intensity. The Cognitive dimension includes items related to
interference with cognitive processes, such as the ability to concentrate when
hallucinations occur. The Emotional dimension includes items related to one’s emotional
state during a hallucination as well as the severity of negative emotional valence of the
hallucination itself. The total of these dimensions represents an overall severity level.
The three dimensions were empirically determined as the factors comprised by items in
the PSYRATS (Haddock et al., 1999). Items in the CHAT specific to auditory
hallucinations partly overlap with PSYRATS auditory hallucination items, and the 0-4
scoring structure of PSYRATS has been implemented in CHAT severity items.
However, these 3 dimensions may or may not be the optimal approach (Woodward et al.,
2014), so researchers may wish to devise alternative dimensional categories from CHAT
items.
Multiple Sensory Modality Assessment
The meaning of having hallucinations in one modality versus more than one
modality, or one modality versus another, is not known. The CHAT can yield scores for
each sensory modality in which interviewees report having hallucinations. This feature of
the CHAT supports efforts to further understand symptom heterogeneity. This also
permits flexible usage, such that a researcher may only inquire about a selected group of
sensory modalities. When considering scores across sensory modalities, however, it is
important to note that there is slight variation in the number of items for the Physical
severity subscale across the modalities (see Summary Score Sheet where this is most
clearly laid out). Hence, in addition to the unclear nature of having one, two, or several
types of hallucinations, the absolute value of the CHAT scores for each modality are not
comparable due to the discrepancy in number of items. Conversion of raw scores to a
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CHAT USER GUIDE
percentage of total possible points would be one way to make the scores across
modalities comparable, if desired. Next, it is not clear that adding scores ACROSS
sensory modalities (such as Current Auditory Hallucination Severity + Current Visual
Hallucination Severity) is meaningful, nor that adding scores for Current and Past/Worst
is meaningful within a sensory modality, and therefore such totals are not included on the
Summary Score Sheet or advised.
Time Frame
The CHAT is designed to assess both current and past hallucination severity, and
it is optional to select only one of these, or to use both.
For Current severity, interviewees are directed to think of “the last couple of
days.” The Current rating is intended to assess the person’s ongoing hallucinatory
experience around the time of the interview. The phrase “last couple of days” may be
interpreted differently by different people, but is a reasonable selection given variation
people will have in their ability to accurately remember experiences under a more rigidsounding time boundary, such as “last 48 hours.”
Past/Worst ratings are recommended to refer to the time period when the
interviewee felt the most distressed by hallucinations or when hallucinations seemed to
cause the most problems. The intent is to capture the height of hallucination severity that
the person has ever subjectively experienced, which may be useful, for example, in
determining underlying pathology severity irrespective of treatment responsiveness. If
the current time is also considered by the interviewee to be the worst time, then the
current and past ratings will be identical.
Selecting One Hallucination Within a Modality
If the interviewee reports multiple hallucinations within a modality, select only
the most significant one to rate, i.e., that which is most frequent, dominant, bothersome,
etc. Information about the occurrence of hallucinations NOT rated can be captured in the
Chronicity Rating Page (further instructions under “Administration Instructions”).
Sources of Information for Ratings
There is no specific recommendation regarding source of information to be used
beyond the interview itself. If collateral information is available, it can be combined with
the information elicited from the interview to make the ratings. The sources of
information used to inform the rater’s judgment can be indicated at the top of the
Screening and full Follow-up forms. In general, raters should use their judgment to
assign scores to items.
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CHAT USER GUIDE
ADMINSTRATION INSTRUCTIONS
Overview
The CHAT sections are:
1. Preliminary Questions
2. Modality Screening
3. Follow-up
a. Lifetime History
b. Severity Scales
c. Substance Use
d. Medication Effects
e. Additional Qualitative Items
4. Impression
5. Chronicity
Each user must decide which sections to use to suite their purposes.
All items on the CHAT should be asked verbatim initially. Such parts are printed in bold
on the CHAT forms.
Guidelines for Each Section:
1. Preliminary Questions: Optional section. Raters must ensure that rapport has been
built prior to administration of the CHAT, such as would occur in a clinical or
assessment interview involving diagnostic instruments. If the CHAT is the first
instrument being administered, Preliminary Questions should be asked to assist in the
rapport-building process and begin gathering pertinent general information. Some or
all may be asked. Additional rapport-building questions may be asked as needed.
The Preliminary Questions do not contribute to any CHAT score.
2. Modality Screening: These are sets of screening questions for the following sensory
modalities: Auditory, Visual, Olfactory, Tactile, and Gustatory. Each set begins with
questions related to more common misperceptions and ends with questions associated
with more pathological experiences. The screening questions are used to assess
whether an individual has ever experienced a hallucination or other type of perceptual
abnormality that is outside normal limits. Items from each set of screening questions
for each sensory modality must be administered, but can be discontinued once the
interviewer is convinced there is sufficient indication that the interviewee has
experienced probable hallucinations and that the follow-up questions will be asked
for that modality. Similarly, if previous clinical interview or rating instruments were
administered which already revealed probable hallucinatory experiences, then the
screening module can be skipped altogether. A box at the top of the screening
module allows for recording of any sensory modality hallucinations already reported,
in which case CHAT screening questions for that modality are not needed.
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CHAT USER GUIDE
Conversely, all questions from each screening module should be asked if the
interviewee continues to indicate no probable hallucinatory experiences. If an
interviewee’s responses on screening questions suggest probable hallucinatory
experience, or if it is unclear, then the follow-up questions should be asked as this
may help clarify whether their experience is hallucinatory.
3. Follow-up: Administer the follow-up question sets indicated from the Modality
Screening. The core follow-up questions are the Lifetime History and the Severity
Scale items. If only this quantified information is desired, the CHAT-Lite form can
be used.
a. Lifetime History
In this section, the onset and recency of hallucinatory experiences is ascertained,
as well as a sense of the number and characterization of different types of
experiences within the sensory modality. This section helps raters determine
which experiences will be assessed for the severity scale items.
b. Severity Scale Items
Follow-up questions include 3-6 questions per severity subscale (Physical,
Cognitive, Emotional) and should be rated according to the criteria in each item.
Tallies of scores from these items constitute the main quantitative severity ratings
of the CHAT. These items are numbered by their sensory modality (AH, VH,
etc.), subscale (P, C, or E for Physical, Cognitive, Emotional), and item number
within the subscale.
i. Physical Severity: Includes items such as Frequency, Duration,
Sensory Intensity, Complexity, and Interference.
ii. Cognitive Severity: Includes items such as Interruption of Thought
Processes and Controllability.
Note: The “Frequency of Control” item is recommended to carefully
separate coping behavior from actual experience of “control.” For
example, putting on headphones to listen to music may be a method of
coping, but is different from the experience of actually being able to
mentally control the experience, which is what this item is intended to
quantify. A question on what the participant is able to control, and a
question on what an interviewee may do to cope, follows the
“Frequency of Control” item to help clarify these concepts.
iii. Emotional Severity: Includes Amount of Negative Content, Degree
of Negative Content, Frequency of Negative Emotion Associated with
Hallucination, and Intensity of Emotional Impact.
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CHAT USER GUIDE
Note: The “Degree of Negative Content” item on the full CHAT (not
the CHAT Lite) is followed by a check-box for “content is definitively
pleasant” to help clarify when this occurs (item would be rated a 1 if
yes, 0 if no). The “severity” of only “pleasant” hallucinations is
unclear but can at least be recorded in this way.
Words and phrases from the different rating levels should be offered to
interviewees to select a rating. Raters should feel free to clarify and follow-up for
all portions of the CHAT to elicit the information needed.
Example 1:
Item AH-CDS1
INTERVIEWEE: “Yeah, I have a little trouble concentrating when I hear the
voice.”
ADMINSTRATOR: “OK, so from the choices of ‘a little, a moderate amount, or
a lot of trouble’ you would say…?”
INTERVIEWEE: “A little.”
Example 2:
Item VH-ESD2
INTERVIEWEE: “Sometimes the people standing there don’t seem evil.”
ADMINISTRATOR: “Would you say they seem evil more than half or less than
half of the time?”
The full CHAT Follow-up form includes the Lifetime History and Severity items
described above, along with additional sections that assess other information often of
interest, including:
a. Substance Use
Assesses whether hallucinations occur only in association with substance use in
that modality. The form advises to skip further follow-up questions if the
hallucination does not occur except in association with substances, but this
determination can be made by each CHAT user.
b. Medication Effects
Medication use and its effectiveness for hallucinations are assessed in this section,
including qualitative information regarding what features of hallucinations
improved, if any. Interviewees are then categorized in a manner adapted from the
Clinical Global Impressions Improvement scale (Guy, 1976), ranging from
responder-to-nonresponder, both currently and over the lifetime. Interviewees are
not required to specify whether it was antipsychotic medication that seemed
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CHAT USER GUIDE
helpful (or not helpful). However, the CHAT does presume this section on
medication effects is largely related to antipsychotic medication given its
indication for psychosis, which includes hallucinations. It also includes an option
to indicate that antipsychotic medication has not been tried. Again, as with all
sections and per discretionary use of each CHAT user, collateral clinical
information may be considered in addition to self report for this section.
c. Additional Qualitative items
These are a series of items that allow further characterization of hallucinatory
experiences. These are not scored or weighted in the severity dimensions, but
may be of further clinical or research interest.
Note: The “Familiar/Unfamiliar” qualitative items are designed to assess
whether the hallucination is personally relevant, e.g., is a voice of a family
member, is a vision of something from childhood, is a scent from a specific
memory. A hallucination is NOT considered familiar just because the participant
possesses semantic knowledge of it, e.g., a voice identified as a supernatural
entity such as God or the devil is considered not familiar for this item; a scent of
rotting meat is not familiar, unless linked to a specific memory such as “it’s just
like grandma’s barn which always smelled like rotting meat.”
4. Impression
After follow-up questions for each relevant sensory modality have been completed,
interviewers can use this section to rate whether or not an interviewee’s reported
experience constitutes a hallucination (see definition earlier in this Guide). The
Impression is a judgment that provides categorization of the interviewee’s
experiences as “definitely a hallucination” that may be useful for research or clinical
purposes as fitting the definition of hallucination or not, as there can be cases in
which it is not clear whether the unusual experience being described constitutes a
hallucination or not until the end of the follow-up questions.
5. Chronicity
The Chronicity table allows an interviewee’s experiences to be rated as chronic,
sparse, and/or once or twice, for each sensory modality. This serves as an additional
manner of capturing hallucination heterogeneity. Raters should indicate all that
apply, as within one modality someone may report both a chronic hallucination as
well as a sparse one. For example, someone may report hearing a voice commenting
in an ongoing way over many years as well as having heard dripping water a few
times over the course of a few months. For this, a rater would circle 3 (“meets
criteria”) in both the Chronic and the Sparse sections for Auditory, and would circle 1
(“no”) for the Once or Twice Auditory section. Hence, for each cell in the table, one
number should be circled.
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CHAT USER GUIDE
Order of Rating Current and Past/Worst
There is no suggested rule regarding what order to rate different time points.
Some interviewees may do better when going through all items for one time period, then
revisit items while focusing on another time period (e.g., first rate past hallucination
experiences, then current). However, some interviewees do better rating both current and
past experiences simultaneously. Raters should use their judgment to select the best
approach for each interviewee if both time points are desired.
Scoring the Severity Dimensions
Transfer scores circled for each severity scale item to the Subscale Scoring Sheet.
Totals can be compiled which comprise the scores for each dimension of severity
(Physical, Cognitive, Emotional). These dimensional severity scores can be summed for
a Total Severity score. Dimensional and Total scores are calculated for each time point
(Past or Current) separately.
VH P OH C OH P TH C TH P GH C GH P
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CHAT USER GUIDE
Relation to PSYRATS-AH
The CHAT Auditory Hallucination scale for Current severity is highly similar to
PSYRATS-AH and correlates highly with it (r = 0.9). Differences were employed in the
CHAT to improve conceptual consistency of the scale and to capture properties of
hallucination experiences estimated to be associated with underlying neurobiological
processes, although CHAT may be useful for other purposes, as well. Differences from
PSYRATS include:
1) the CHAT has altered criteria relative to PSYRATS for assigning 0-4 for some
items, to improve parallelization on CHAT items (e.g., a score of 0 on all items
indicates an unqualified “not present”)
2) criteria alterations for each 0-4 score were altered in some CHAT items from
PSYRATS items to ensure that higher numbers in each item indicate a more
universally-agreed-upon indication that higher numbers are an increased in
severity
3) the CHAT omitted some PSYRATS items that relate less directly to features of
the hallucination experience
Specific departures from PSYRATS-AH, as generally described above, include:
1. Alteration of scoring criteria
a. Frequency item: In CHAT, a 0 indicates “not present” whereas for
PSYRATS a 0 indicates “not present or present less than once a week”.
CHAT moved “less than once a week” to receive a score of 1, and at least
once a week to a 2, and so on.
b. Controllability item – 0 means “no hallucinations present” and 1 is the
item to indicate “always has control.” CHAT calls this item “Frequency
of Control.”
2. PSYRATS-AH items not in CHAT
a. “Location”
b. “Beliefs regarding origin of voices”
c. “Disruption to life”
3. CHAT items not in PSYRATS-AH
a. Intensity of the sensory nature of each experience (loudness, vividness,
etc.)
b. Complexity (assessing the completeness of the experience as a percept)
c. Interference with other stimuli in that modality
d. Interruption of thoughts/concentration (ranges from none to severe)
e. Attentional demand (how difficult it is to ignore the experience)
To obtain a PSYRATS-AH score from the CHAT-AH Current severity items (which may
be desirable for optimal comparison to prior studies), raters need only add on the 3
omitted PSYRATS-AH items and ensure that scoring of the PSYRATS-AH Frequency
and Controllability items follows the PSYRATS-AH scoring scheme for them. All other
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CHAT USER GUIDE
scores from CHAT-AH Current can be transferred to the comparable PSYRATS-AH
item.
Limitations
The CHAT is largely a self-report instrument and so with it come the usual concerns
around reliability. Next, the CHAT focuses on quantifying a mental experience not
directly observable by others, a departure from instruments such as the PANSS
“hallucination behavior” item, which includes consideration of more objective
observation (although not exclusively). Lastly, the range of features of hallucinatory
experiences is not comprehensively captured by the CHAT. Additional important
features may have been missed that are relevant to different type of research or clinical
questions.
Psychometrics
See attached presentation, cite as:
Kern et al., (2015) Exchange the magnifying glass for a microscope: The Chicago
Hallucination Assessment Tool (CHAT). Schizophrenia Bulletin, 41(suppl 1)., S110.
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CHAT USER GUIDE
REFERENCES
Andreasen, N. C. (1984). Scale for the assessment of positive symptoms (SAPS) University of Iowa. Iowa
City, IA.
Guy, W. (1976). Clinical Global Impressions. In: ECDEU Assessment Manual for Psychopharmacology,
revised. National Institute of Mental Health: Rockville, MD. pp 218–222.
Haddock, G., McCarron, J., Tarrier, N., & Faragher, E. B. (1999). Scales to measure dimensions of
hallucinations and delusions: The psychotic symptom rating scales (PSYRATS). Psych Med,
29(4), 879-889.
Woodward et al. (2014). Symptom dimensions of the psychotic symptom rating scales in psychosis: A
multisite study. Schizophr Bull, 40, S265-274.
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